(a) Field of the Invention
The present invention relates to an apparatus and a method for hot bonding metal plates. More particularly, the present invention relates to an apparatus and a method for hot bonding metal plates having advantages that removing an oxidation film of the metal plates and bonding the metal plates are simultaneously accomplished and a bonding force between the metal plates is enhanced by applying a strong bonding pressure to the metal plates.
(b) Description of the Related Art
Generally, a welding method is well known as the method for bonding two metal plates. However, if the metal plates are thick or materials of the metal plates are different from each other, it is difficult to bond the metal plates with the welding method. Especially, in a hot rolling process, thick moving metal plates need to be rapidly bonded so as to continuously roll the metal plates. Thus, a welding method is rarely used in the hot rolling process.
Therefore, a bonding method is used for bonding the metal plates in the hot rolling process. However, an impurity, such as an oxidation film, coated on bonding surfaces of the metal plates needs to be removed according to the bonding method. Therefore, an additional, preceding process for removing the oxidation film is required.
Recently, a method for removing the oxidation film and simultaneously bonding the metal plates has been investigated.
For example, a method for overlapping two metal plates that are not cut and then bonding the two metal plates by applying a pressure with upper and lower cutting blades having a triangular-prism-shaped protrusion portion in an inclined direction to the normal of the surface of the metal plates is disclosed in Korean Patent Laid-open Publication No. 2001-0062404. In this case, the metal plates are clamped by the triangular-prism-shaped protrusion portion and the bonding surfaces are compressed by the triangular-prism-shaped protrusion portion so as to enhance the bonding force between the metal plates. In addition, since the bonding surfaces of the metal plates are formed along the inclined direction to the normal of the metal plates' surface, the metal plates are bonded well in a successive rolling process.
However, if the metal plates are clamped by the triangular-prism-shaped protrusion portion, the pressure applied to the bonding surfaces may be low and flaws may occur at the metal plates.
In addition, a method for respectively forming protrusions and depressions as the slanted shape at the two metal plates and tightly fitting the protrusions and depressions of one metal plate to the protrusions and depressions of the other metal plate so as to enhance the bonding force is disclosed in Korean Patent No. 0293284.
However, an additional process for forming the protrusions and depressions may be needed and a sufficient pressure for bonding the metal plates may not be obtained since the protrusions and depressions are formed as the slanted shape.
A method for fixing the two metal plates by clamps, cutting the metal plates with reference to one clamping surface, and then applying a bonding load to a bonding surface is disclosed in Korean Patent No. 0382011.
As described above, most methods for bonding hot metal plates are such that a cutting surface is formed at a front portion of the metal plates and simultaneously a pressure is applied to the cutting surface of the metal plates by a clamp.
To bond the front portion of the metal plates, the cutting surface is formed by a cutting mold and the bonding pressure is applied to the cutting surface by a simple clamping operation according to the method described above.
According to the method described above, the pressure may not be applied horizontally to the front portion of the metal plates since the length of the metal plates are longer than the width of the metal plates. Therefore, the metal plates are overlapped instead of confronting the front end of the metal plates and the cutting load is applied to the overlapped metal plates so as to bond the metal plates. For example, in a state that the two metal plates are fixed by the clamp, the pressure is applied to the metal plates in the normal direction of the metal plates' surface so as to cut the metal plates and apply the bonding pressure along the surface of the metal plates. In this case, since the metal plates are cut and simultaneously bonded, an impurity, such as an oxidation film, may not be inserted into the bonding surface of the metal plates. However, since the metal plates are bonded just by the cutting and clamping force, the bonding pressure that is applied to the bonding surface in the normal direction of the bonding surface may be weakened. To solve this problem, many researches related to improving the shape of a cutting blade have been made.
In contrast, a method for overlapping front surfaces of the metal plates and then forming a bonding surface at the overlapped surfaces is disclosed in Korean Patent No. 0261204. According to this method, after an oxidation film of a bonding surface is mechanically removed by a reducing flame, the metal plates are bonded by pressing bonding portions of the metal plates.
However, a preceding process for removing the oxidation film so as to bond the overlapped surfaces of the metal plates is required and a trimming process may be performed since metal is pushed out in the width direction and a width of the metal plates are widened.
In cases that the metal plates are bonded with a strong forging pressure instead of cutting the metal plates, the bonding pressure may be strong. However, many problems may occur such as that a preceding process for removing the oxidation film coated on the bonding surfaces of the metal plates may be performed and the additional trimming process may be performed since the metal is pushed out in the width direction and the width of the metal plates are widened. To solve these problems, the metal plates are formed such that a width of the overlapped portions of the metal plates is narrower than that of the other portions of the metal plates. Therefore, in this case, an additional trimming process is not needed
However, in this case, an additional process for narrowing the overlapped potions of the metal plates may be performed.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.